ORGANIC DEPENDENCE AND DISEASE 
33 
thusiasm, for no service to this science, whether in fact 
or philosophy, is more competent or more needed than 
the evidence which lies here buried. To Walcott, who has 
lifted the veil from the unsuspected specialization of the 
Cambrian fauna and, with Barrande, has taught us to re- 
gard that fauna, not as primitive but a venerable monument 
of life, we owe our best knowledge of life in the still earlier 
ages. 
Out of the vast Precambrian ages and its great seas 
which, in view of the high specialization of the rich Cam- 
brian fauna, must have laid down fossiliferous sediments 
for inconceivable ages, we know immense growths of lime 
deposits built up as reefs in the seas like the corals of today 
and in whose formation algal life seems to have played 
effective part. There has also been described a spongelike 
skeleton called Atikokamnia (A. lawsoni and A. irregularis 
Walcott) from the Steeprock series of Ontario, an organism 
so primitive in its skeletal characters that its reference even 
to the sponges lies in doubt . 1 
Walcott 2 has described as “Micrococcus sp. indet.,” a 
bacterium from the Algonkian (Precambrian) of Gallatin 
county, Montana, which the bacteriologist Kligler 3 regards 
as close to the existing Nitrosococcus which derives its ni- 
trogen from ammonium salts. “The cell structure of the 
Algonkian and of the recent Nitrosococcus bacteria is very 
primitive and uniform in appearance, the protoplasm being 
naked or unprotected. ” With this point before us we are 
confronted by the impressive inference that this simplest 
of organic structures has defied change and the ages. The 
type at least has not failed to find its appropriate surround- 
ings or to adjust itself readily to change in them. It is the 
1 It appears from the comments of Walcott that we must not yet regard the 
horizon of this organism finally established, though Van Ilise, Leith and the 
discoverer, Lawson, regard it as from true sediments of the Precambrian Hu- 
ronian. 
2 Proc. National Academy of Sciences, v. 1, p. 256, 1915. 
3 See Osborn’s “ Origin and Evolution of Life,” 1917, p. 85. 
